In the machine tool such as an NC lathe, a machine operation check is performed according to a sequence program by, for example, an operator. At that time, a ladder diagram screen is displayed on an operation panel of the machine tool, and ON/OFF switching of a contact point is performed based on the ladder diagram. Meanwhile, since confirmation of an output state that occurs due to such switching is necessary, the operator switches the display of the operation panel to an I/O monitor screen. Then, first the operator performs the operation confirmation for operation by displaying an operation screen of each machine tool on an operation panel when performing the operation confirmation.